Thermo recording

ABSTRACT

A recording material composed of an opaque dispersion of nonpolymeric fatty or waxy material in a binder containing a pigment that absorbs light and converts it to heat becomes clear in areas exposed to light.

United States Patent lnventor Eric Maria Brlnckman Mortsel, Belgium Appl. No. 677,759 Filed Oct. 24, 1967 Patented Nov. 9, 1971 Assignee Gevaert-Agl'a N.V.

Mortsel, Belgium Priority Oct. 24, 1966 Great Britain 47,626/66 THERMO RECORDING 9 Claims, N0 Drawings US. Cl

1nt.Cl..... Field of Search 96/48, 96/33, 117/l.7, 1 17/356, 250/65, 250/65.1,101/464,l01/453,101/463,101/456, 101/467, 96/36,4,117/36.l

[56] References Cited UNITED STATES PATENTS 3,511,652 5/1970 Vrancken et a1. 96/27 3,514,597 5/1970 Dc Haes et al,. 96/27 X 3,476,937 1/1970 Vrancken.... 250/651 3,121,162 2/1964 Roman et al. 250/651 3,298,833 l/l967 Gaynor 96/27 3,384,015 5/1968 Newman 2511/65.] 3,405,265 10/1968 Vrancken 117/1.7 OTHER REFERENCES Van Der Grinten Bulletin, Thermographic Writing and Copying Methods and Materials," Aug. 8, 1963, pp. l- 6 Primary ExaminerGeorge F. Lesmes Assistant Examiner-R. E. Martin AtlomeyWilliam .1. Daniel ABSTRACT: A recording material composed of an opaque dispersion of nonpolymeric fatty or waxy material in a binder containing a pigment that absorbs light and converts it to heat becomes clear in areas exposed to light.

THERMO RECORDING The present invention relates to a method for recording or reproducing information by means of electromagnetic radiation and to a heat-sensitive element containing substances wherein heat is produced by exposure to electromagnetic radiation.

Various attempts have been made to record printed matter by irradiating printed markings so that they become heated while being in heat-conductive relationship with a heat-sensitive recording material. In other words according to that technique heat is image-wise transferred into the recording material. According to other heat-recording techniques, however, heat is generated in the recording material itself e.g. by electromagnetic radiation absorbed and converted therein into heat, by image-wise or record-wise subjecting it to the Joule effect, or by subjecting it to image-wise modulated high frequency heating. The present invention is concerned with recording methods applying the principle of internal heating of the recording material and contributes to the realization of the production of copies without developing step as well as of the production of liquid-developable records and printing masters.

A preferred method of recording information according to the present invention essentially comprises he following features:

a recording material is information-wise exposed to electromagnetic radiation preferably containing visible light;

the said recording material comprising at least one recording layer containing a binder and a liquid material and/or solid material dispersed in said binder, the liquid and/or solid material being more hydrophobic than the binder and at leats partly forming a compatible mixture with the binder upon heating i.e. an an increase in homogeneity in the mixture consisting of the binder and the liquid and/or solid material is obtained upon heating, the light-transparency of said compatible mixture being higher than that of the dispersion before heat- 8;

the said recording material also comprising a substance or substances, which is or are in heat-conductive relationship with said dispersion and absorb(s) at least part of the radiation that strikes said recording material, thereby causing heating of said recording material;

the intensity and duration of the information-wise applied radiation being such that in consequence of the radiation absorbed in the recording material and the heat energy produced therein a record is obtained in terms of a difference, in transparency and in hydrophility, in which record the more transparent portions correspond with the portions that have been image-wise irradiated and undergone a decrease in hydrophilit The recording material may be composed of one single layer i.e. the recording material may be a self-sustaining layer or sheet. However, the recording material may also be composed of several layers including a support.

I The dispersed liquid material and/or solid material, which is more hydrophobic than the binder, may be composed of one single substance or a mixture of substances. For convenience sake reference is made hereinafter to the hydrophobic material." A dispersed material solid at room temperature C.) is preferred.

The binder may consist of one single binding agent or of a mixture of different binding agents, examples of which are given further on. For convenience sake reference is made hereinafter to "the hydrophilic binder".

in order to determine whether a particular hydrophobic material is capable of forming a compatible mixture with a particular hydrophilic binder, a dispersion of said hydrophobic material in said binder is applied to a transparent support, e.g. a glass plate. At least part of the coated support is then heated to a temperature ranging between 20 to 250 C. beyond room temperature and finally is cooled back to room temperature. If the heat-sensitive layer after having been heated and cooled back transmits at least 10 percent more light than the nonheated material, the dispersion is suited for recording purposes. Preferably a heat-sensitive layer is used, transmitting at least 20 percent more light after heating in the temperature range between 50 and C.

The presence of a dispersing or wetting agent in the dispersion may even accentuate the increase in transmittance. In this respect reference can be made to wetting agents, which are solid at room temperature eg, polyoxyalkylene waxes.

Depending on the type of hydrophobic material and hydrophilic binder an amount of dispersing agent varying between 5 and 30 percent by weight based on the total weight of the recording layer may be present therein.

The required ratio of hydrophobic material to hydrophilic binder in the recording layer depends on the degree of dissolution of the particular hydrophilic and hydrophobic ingredients into each other on heating as well as on the desired degree of differentiation. Preferably the ratio by weight of dispersed hydrophobic material to hydrophilic binder is at least 1:4 and at most 25:1.

As hydrophobic material use is preferably made of a substance or substances that soften(s) or melt(s) between 20 and 250 C. beyond room temperature. In dispersed form the particles preferably size between 0.01 p. and 50 u.

The substance or mixture of substances for yielding heat energy under the action of radiation is or are preferably provided in the recording layer in particle form. Finely divided blackor dark-colored pigments or dyes are very suitable. Although the said substance or mixture of substances is or are preferably provided in the recording layer, e.g. in the hydrophobic thermoplastic material itself, it may as an alternative be added to another composite layer of the recording material, e.g. to an interlayer between the recording layer and the support or to a surface layer covering the recording layer.

The light-absorbing substance or substances may be used in an amount up to 30-50 percent by weight of the total weight of the recording layer, in such an amount that the optical density varies between 0.2 and 5.0, and preferably between 0.2 and 1.0 in the case of a reflectographic exposure. Recording may occur by direct exposure or, provided that the recording material is sufficiently transparent, by reflectographic exposure.

When applying a reflex exposure, the intensity of the exposure must be such in relation to the heat-sensitivity of the recording layer that the light-rays initially incident upon the recording layer, undifierentially over its whole area, do not in themselves suffice to cause heating sufficient to result in a significant reduction of the opacity of any part of the recording layer. The additional heating required for achieving a significant differentiation in transparency is due to the additional heating resulting from reflected radiation.

When recording a graphic original, the record in terms of a difference in transparency of different areas of the recording layer may constitute a laterally reversed or a legible record of the graphic original, depending on the orientation of the recording material relative to the original and the radiation source during the exposure.

Actual contact or a very close relationship of the original to be copied and the recording layer is recommended as favoring the production of well-defined record images. The intensity and duration of the radiation affecting the recording layer are also important factors influencing image quality. To reduce lateral conduction of heat within the recording material the exposure should be as short as possible. Preferably the exposure is not more than 10 second in duration and the best results are obtained with exposures of less than 10 second, e.g. between 10 and 10 second. Such brief exposure times imply the use of high energy radiation sources. Preferably the intensity of the radiation incident upon the recording material is at least 0.1 Watt. see/cm. 2. In the event that the recording material is exposed reflectographically the radiation incident upon the recording material includes radiation first incident upon such material from the radiation source andradiation reflected onto such material from the original.

When using very brief exposure times as above, particularly sharp images" can be obtained even if the recording layer,

' during the exposure, is in surface contact with the light-absorbing markings on the original since the time is too short for the recording layer to be materially affected by heat-conduction from such markings. On the other hand, in the exposed or most exposed areas of the recording material, a sudden and very intense internal heating of the recording material takes place.

For the same amount of light energy it is more advantageous to irradiate the recording material within a period of time as short as possible to obtain a higher local increase of temperature.

For obtaining a higher local increase of temperature it is unnecessary, though allowable of course, to use an exposure time less than 10" second, because as already indicated, good results are obtainable with exposure times up to second. Various types of flash lamps are suitable radiation sources, e.g. gas discharge lamps emitting radiation substantially in the wavelength range of 0.3 ,u. to 1.2 p.. Preferably the radiation employed contains at least 30 percent of the energy in the wavelength range below 700 mp" The performance of the recording method according to the present invention gives in all cases a visible image or record in the form of an image-wise difference in transparency of the recording element, which becomes more transparent in the heated areas.

Although said difference in transparency suffices for a correct and direct reading of the copy it has been observed that together with the increase in transparency in the heated areas of the recording layer a decrease in hydrophility is obtained i these areas.

Together with said differentiations depending on the composition of the recording material a more or less pronounced differentiation in premeability and solubility in a liquid e.g. water or an organic solvent such as methanol and ethanol is obtained.

These differentiations allow the exposed material to be developed in a variety of ways as will be referred to.

hereinafter and the recording material can be applied in a considerable variety of reproduction techniques including e.g. chemical, physical and photomechanical reproduction techniques.

Thus, the invention can be employed in the production of printing masters, such as a planographic printing master, a screen printing master, a hectographic printing master and a hydrotype master.

In the development of the recording material use can be made of the image-wise differentiation in hydrophility, permeability for or solubility in suitable liquids.

Such development methods are detailedly described in the examples.

if the recording layer containing the hydrophobic thermoplastic material is covered by another layer, e.g. by a surface layer containing pigment particles which absorb at least some of the radiation used for the information-wise exposure, this top layer must not prevent the subsequent development step. There are various ways of achieving the required result. By way of example, the top layer may be composed so, that it can easily be removed, e.g. with a solvent for its binder followin g the exposure step, leaving the recording layer in place. The incorporation of the pigment into a top layer, which is removed after the exposure step has definite advantages since the final image quality is improved by the absence of any overall grey tones due to the presence of dispersed pigment. If the top layer is itself permeable for the developer liquid, it can remain in place provided the development step does not result in overall coloration of this top layer. Such coloration can be avoided by using, e.g. a colorless developer liquid containing a color coupler for a component in the recording layer and/or subjacent layer, or a developer liquid containing an ingredient for initiating a color reaction between compounds present in the recording layer and/or subjacent layer. A third possibility consists in the incorporation of light-sensitive silver halide into a sublayer beneath the recording layer so that after exposure, liquid silver halide developer can reach this sublayer to bring about image-wise development via the permeable top layer and the still permeable areas of the recording layer.

Having stated the general concepts of this invention, a detailed description will now be made of the composition and the structure of heat-sensitive materials, types of radiation sources and exposure techniques suitable for use in carrying out the present invention.

As hydrophilic binding agent for the heat-sensitive layer hydrophilic natural colloids, modified hydrophilic natural colloids and synthetic hydrophilic polymers can be used. The hydrophilic binding agent should not necessarily be watersoluble, so that use can be made of colloids or hydrophilic polymers such as, e.g., ethylcellulose and methylcellulose of low methoxy substitution degree.

Suitable water-soluble binding agents are e.g. casein, zein, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, carboxymethylhydroxyethyl-cellulose, starch derivatives such as hydroxyethylstarch, and hydroxypropylstarch, sucrose octaacetate, ammonium alginate and hydrophilic derivatives of such colloids, synthetic water-soluble hydrophilic polymers e.g., poly(N-vinyl pyrrolidone), polyvinylamine, polyethylene oxide, polyacrylic acid and hydrophilic copolymers and derivative of such polymers.

As partly water-soluble or water-insoluble polymers are particularly mentioned the cellulose derivatives that contain an insufficient amount of water-solubilizing substituents, such as partly etherified or esterified cellulose e.g. belonging to the group of ethylcellulose, benzylcellulose, hydroxyethylcellulose acetate, cellulose acetate sorbate, cellulose acetate butyrate, and further vinyl polymers containing hydrophobic and hydrophilic recurring units (e.g., containing a carboxy, hydroxy or sulpho group), e.g. copolymers of vinyl acetate and crotonic acid, copolymers of ethylene and vinyl acetate, prepolymers of diallyl phthalate, poly(diallyl o-phthalate), copolymers of cumarone and indene, copolymers of styrene and allyl alcohol, polyvinylbutyral containing unacetalized hydroxyl groups, copolymers of vinyl chloride, vinyl acetate and maleic anhydride, copolymers of vinylidene chloride, acrylonitrile, copolymers of vinyl stearate and vinyl acetate, and copolymers of hydrophilic vinyl compounds, styrene and/or a-methylstyrene e.g. copolymers of methyl acrylate and styrene, and copolymers of styrene and acrylic acid.

Other suitable binding agents are e.g. sandarac, colophony, pyrogenated copal resin and shellac resin.

In. order to prevent a misunderstanding of the relation of the hydrophilic binding agent and the dispersed liquid or solid hydrophobic material in the recording layer for use according to the present invention, it should be stressed that the binding agent has to be more hydrophilic or more wettable with water than the said dispersed material.

As hydrophobic liquid or solid substances (solid at room temperature) for composing the hydrophobic dispersed phase use can be made of e.g. paraffins e.g. petrolatum, liquid or solid fatty acids e.g. oleic acid, stearic acid and adipic acid, alcohols e.g. lauryl alcohol and n-hexadecyl alcohol and waxlike substances, so waxes in the broadest sense of the word.

Thus, waxes of the known six classes i.e. vegetable, mineral, insect, petroleum, animal and synthetic waxes can be used.

Carnauba wax, ouricury wax, candellila wax, japan wax, and sugar cane wax, which belong to the vegetable wax class; ozokerite, montan wax ceresin, and utah wax, which are mineral waxes; beeswax, and Chinese insect wax, which belong to the insect class; paraffin wax, which is a member of the petroleum class; spermacetic wax from the sperm whale which wax is of the animal class, may be used. These waxes, e.g. ceresin, can be mixed with oil.

Vegetable, insect, and animal waxes are usually composed of a mixture of various high-melting fatty acids, alcohols, and esters.

Chemically modified natural waxes such as the IG waxes made from the natural montan wax can also be used. Another modified natural wax is a partly oxidized paraffin that can be a substitute for camauba wax. Castor wax and Opalwax are waxes obtained from hydrogenated castor oil.

Further synthetic waxes are e.g. those solid under the trade names Acrawax, Armid, Voltalef, and Carlisle wax.

Acrawax" is a registered trade name of Glyco Chemicals, New York, NY. U.S.A.) for complex nitrogen derivatives of the higher fatty acids.

ARMID" is a registered trademark of Armor Industrial Chemical Company, Chicago, Ill, U.S.A. for a waxlike material containing fatty acid amides.

Voltalef" is a registered trade mark of PechineySt. GobainParis-France for chlorineand fluorine-substituted hydrocarbons.

Carlisle" is a registered trade mark of Carlisle Chemical Works, U.S.A. for synthetic waxes, the physical constants of which are mentioned in Bennett I-I., Industrial waxes, Vol. I Natural & Synthetic waxes (1963) Chemical Publishing Corp., New York, U.S.A.

Detailed information of many types of waxes can be found in the above-mentioned book of Bennett 11., The Chemistry and Technology of Waxes by Albin H. Warth 2nd Ed, Reinhold Publishing Corp., New York, and Chemie Lexikon by Rompp I-I., Band II, F ranckhsche Verlagshandlung Stuttgart.

Use can also be made of monomeric organic hydrophobic substances, e.g. aromatic compounds which are sparingly or not soluble in water eg biphenyl, o-terphenyl, naphthalene, anthracene, terpene compounds and derivatives thereof, e.g., camphene, camphane, and camphor. Higher aliphatic aldehydes, ketones, ethers, esters, e.g., sucrose distearate, sorbitol tristearate; ehtylene glycol monohydroxystearate, glycerol monostearate and diethylene glycol stearate, nitrogen containing hydrophobic organic compounds of the class of the amides, anilides, and thio compounds, e.g., biphenylsulphone and thionaphthenequinone. Halogenated organic compounds such as a-bromocamphor, carbon tetrabromide, trichlorobenzene, hexachloroethane, and iodoform.

In preparing. the recording materials according to the present invention the hydrophobic material, which has proved to form a useful combination with a selected more hydrophilic binder, is dispersed in a solvent for said binder preferably together with the radiation-absorbing substances converting radiation into heat. The binder may be dissolved in the dispersing liquid after or before the hydrophobic material is dispersed therein.

As appropriate solvents can be mentioned, e.g., water, methanol, ethanol, acetone, methylene chloride, diethyl ether, cyclohexane, cyclohexanone, dioxane, toluene, and mixtures of these solvents.

The hydrophobic particles in dispersion may size from 0.0lp. to 5011., However, the larger the particles, the less the resolving power on recording. Very good results are obtained with dispersions, the dispersed hydrophobic particles of which size form 0.05 p, to 2,1,. Dispersions wherein the dispersed particles size from 1/1. to Imp. are considered as colloidal systems, which can be obtained in a colloid mill or by means of an ultrasonic wave generator.

In connection with radiation-absorbing substances, pigments or dyes converting absorbed radiation into heat, reference can be made to the Belgian Pat. Specification 68l,l38 filed May 17, 1966 by Gevaert-Agfa NV. and the U.K. Pat. Specification 1,076,799 filed Dec. 22, 1964 by Agfa AG.

Particularly suitable substances for use according to the present invention and which convert radiation, e.g., visible light into heat, are, e.g., carbon black, graphite, oxides or sulfides of heavy metals, particularly of those heavy metals having an atomic weight between 45 and 210, such as iron oxides, manganese or lead sulfide, or these heavy metals themselves in finely divided state e.g., silver, bismuth, lead, iron, cobalt, or nickel. Carbon black is preferred because of its high radiationabsorptive character, heating power, and low cost.

The substances converting absorbed radiation into heat may be present in the hydrophilic binder and/or in the hydrophobic material.

In addition to the already cited ingredients the coating composition for forming the recording layer may also contain other ingredients, e.g., dyes, reaction components for the formation of dyes, catalysts for color reactions, metal particles that can be dissolved or etched away, development nuclei, light-sensitive substances, e.g., light-sensitive silver halide, developing agents for exposed silver halide, hardening agents, softening agents, fluorescent compounds, and fillers, e.g., hydrophilic fillers such as silica, zinc oxide barium sulfate and other substances suited for filling purposes.

These ingredients may also be incorporated into a waterpermeable top-coating on the recording layer or into a subjacent layer.

Dyes may be present in dissolved or dispersed form. They can advantageously be applied in dispersed form and selected in such a way that they dissolve in the melted hydrophobic material.

The thickness of the recording layer preferably varies between 0.2 1. and p.

The support may be hydrophobic or hydrophilic and may be porous or nonporous. Thus, use can be made of e.g., supports of paper, natural, modified natural or synthetic resins, metal, glass and the like. According to a preferred embodiment the support is contrasting in color in respect of the recording layer so that the image-wise change in transparency of the latter is detected as a difference in color between the image and nonimage areas.

Before giving detailed examples for practising the method of the present invention, a short survey is given of different systems, which are suited for the manufacture of copies and masters for the reproduction of originals starting from the heat-sensitive recording material according to the present invention. This survey is intended for illustrating the possibilities and advantages of the invention without limiting therefore the scope of this invention.

According to a first application the image-wise irradiated and consequently heated recording material, which then contains a reproduction of the original in terms of a different transparency of different portions of the recording layer, can be used as a legible document or can be applied as a transparency in diazo-type printing with ultraviolet radiation.

According to a second application the image-wise differentiation in water-permeability can be utilized for moving by diffusion image-forming substance or substances into the recording element in correspondence with the nonheated areas, the water-permeability of which is not decreased. For instance the image-wise exposed recording material is dipped into an aqueous dye solution, so that the dye can diffuse into the recording element (layer or sheet) only at the areas that remained water-permeable. A solution of a catalyst that initiates a color reaction between components in the recording material or a solution of a colorless reaction component capable of entering into a color reaction with a colorless or slightly colored reaction component in the recording material can be used instead of a dye solution.

By way of another example of the second application, it is also possible to incorporate into the recording element colored substances that can be bleached out and are bleached by a bleaching agent diffusing into the areas of the recording layer that remained permeable. Alternatively, metal particles e.g., colloidal silver can be dispersed homogeneously in the recording element and image-wise etched away or dissolved by a suitable liquid penetrating into the water-permeable areas.

According to a further alternative of the second application an image-forming substance incorporated into the recording material is transferred by diffusion from the areas that remained permeable to an image-receiving material. Thus, it is possible, e.g., to incorporate into the recording material silver salts, that can be complexed, and in their complexed form can diffuse to a receiving material containing reduction nuclei or development nuclei, on which in accordance with the areas of the recording layer that remained permeable, silver is deposited image-wise. It is self-explanatory that the recording material and/or the receiving material may contain (a) developing substance(s) to reduce silver salts. it is also possible to add a dye, which on moistening of the recording material can be leached out gradually through the permeable areas and transferred to a receiving sheet.

According to a particular embodiment of the second application substances of the image portions of the recording layer that remained hydrophilic can be transferred to an imagereceiving material by bringing the latter in contact with the exposed recording layer either or not in the presence of this processing liquid an afterwards separating the materials from each other. During or immediately before the transfer step moderate heating may be applied to the recording and or the receiving material.

According to a third application, which may be applied in those cases wherein the heated portions of the recording layer are rendered insoluble in a suitable liquid, or the solubility of which in this liquid is strongly reduced, an exposed recording layer containing, e.g., a water-soluble binder is treated with water or an aqueous liquid in order to wash away nonheated portions, thus leaving a relief image. If according to this third application the recording layer contains a pigment or a dye, the relief image forms a colored pattern of the original. lf the heat-sensitive recording layer composition is applied to a screening material, e.g., a Japan paper, a nylon fabric, or a support of woven bronze wire, a screen-printing master (stencil) can be produced after washing away the water-soluble portions. In certain cases it is possible to omit the removal (by washing) of the permeable portions of the recording layer prior to printing when the printing ink along can permeate and/or dissolve the nonheated portions of the recording layer.

According to a fourth application of image reproduction, which is based on the obtained hydrophilic-hydrophobic image differentiation, the exposed recording layer possessing such differentiation, in a sufficiently strong degree is used as planographic printing master. in combination with such a master a common offset-ink or a hydrotype ink e.g., an ink as described in the Belgian Pat. Specification 676,898 filed Feb. 23, 1966 by Gevaert-Agfa N.V. may be used.

According to a preferred embodiment of the present invention the exposure is carried out with a xenon gas discharge lamp, which can supply an energy of ZOO-2,000 Watt.sec. in a period of 10" to 10 seconds, the energy that impinges on the recording layer preferably varying between 0.5 to 1.5 Watt.sec. per sq.cm.

According to a preferred arrangement the discharge lamp is in the form of a thin tube fitted in a hollow glass cylinder in order to make possible a uniform exposure of the recording material applied according to the periphery of the cylinder. More details about such a gas discharge lamp can be found in the Belgian Pat. Specifications 664,868 filed June 3, 1965 by Agfa-Gevaert AG and 681,138 filed May 17, 1966 by Gevaert-Agfa N.V. The intensity of the light emitted by such a gas discharge lamp is particularly high in the region of the visible spectrum.

it is possible to employ a number of flash tubes operating simultaneously, or to obtain a suitable image differentiation by flashing a single tube at suitable intervals. Reflectors and other optical components may be included to provide irradiation of maximum uniformity.

Radiation sources with a much lower energy output than the aforementioned may be used if the light energy is focused onto a relatively small heat-sensitive area, e.g., by using a laser beam or by carrying out the exposure progressively and/or intermittently. In other words, the heat-sensitive material containing the radiation-absorbing substances, which convert the radiation, e.g., light, into heat, may be scanning-wise exposed, e.g., light, into heat, may be scanning-wise exposed, e.g., by means of an image-wise modulated high-intensity light spot, and may be progressively exposed e.g., through a slot wherein light, e.g., ofa tubelike radiation sources, is focused.

Obviously, the heat-sensitive material, can be integrally heated before or during the image-wise heating, to a certain temperature below the temperature at which a material increase in transmittance is obtained.

The following examples illustrate the present invention without however limiting it thereto.

EXAMPLE 1 A mixture consisting of ethylcellulose 30 5. carbon black 0.5 g. methanol 400 is ground for 6 hours in a ball mill. To this fine suspension a dispersion is added obtained by grinding in a vibrating ball mill for 2 hours a mixture consisting of:

carnauba wax 50 g. zinc stearate 2 g. methanol 500 cc.

The mixture obtained is then coated on a subbed support of polyethylene terephthalate in a proportion of 60 g. per sq.m. After having been dried at room temperature the layer has a grey and opaque appearance. Then the material is laid with its heat-sensitive layer on an original to be reproduced and the whole is reflectographically irradiated with an electronic flash lamp, the energy output of which amounts to 0.75 Watt.sec. per sq.cm. Hereby the heat-sensitive material becomes transparent on the areas corresponding with the white areas of the After drying a heat-sensitive layer is applied thereto in a proportion of 50 g./sq.m. from a composition, which is obtained by grinding for 6 hours in a ball mill the following substances:

ethyl cellulose 35 g.

carbon black 0.5 g.

ethanol 400 cc.

and added to a mixture of the following substances:

stearic acid 65 g.

morpholine 3 cc.

ethanol 400 cc.

which mixture has been shaken previously for 2 hours in a vibrating ball mill. As in example 1 the heat-sensitive master obtained is now reflectographically exposed with an electronic flash light, the energy output of which amounts to 0.45 Watt.sec/sq.cm. The master is then inked with an aqueous composition consisting of:

low viscosity cnrboxymethylcellulose 90 g. water 900 cc. aqueous carbon black dispersion conmining per I00 g. 53 g. ofcnrbon black. 23 g. of water, 18 g. otglycol, and 6 g. of nonyl-phenol-ethylcne oxide condensate 50 g.

By pressing this inked master against a sheet of common paper a black positive print is obtained from the original. The inking and copying steps can be repeated at will so that up to [00 prints.

EXAMPLE 3 A subbed cellulose triacetate support is coated in a proportion of g./sq.m. with the barium sulfate dispersion of example 2. After drying at heat-sensitive layer is applied thereto in a copoly(vinylidene chloride/acrylonitrile/ n-butyl acrylatelethyl acrylate) (86/3/7/4! by weight) 60 g. carbon black having a particle size of 0.01 p 0.5 g. oleic acid 20 g. methanol 800 cc.

This material is reflectographically irradiated with flashlight as described in example 1. A positive transparency is obtained.

EXAMPLE 4 A transparent paper support of 40 g./sq.m. is coated in a proportion of 50 g./sq.m. with a dispersion consisting of:

cthylcellulose (degree of substitution of ethoxy groups 2.45) 20 g. carbon black 0.5 g. glycerol monostearate 80 g. methanol 800 cc.

and which dispersion has been ground for 8 hours in a ballmill.

After the exposure as in example l a positive transparency is obtained. EXAMPLE 5 Example 4 is repeated but the heat-sensitive material is reflectographically exposed with its backside facing the original. The material is then inked with an ink composition consisting of 20 percent aqueous methylene blue. inking is carried out by means of an offset-roller. Since the ink is only accepted at those areas corresponding with the text parts of the original, a direct-reading positive print is obtained. EXAMPLE 6 A subbed support of polyethylene terephthalate is coated with a baryta suspension as described in example 2. Then a coating is applied thereto in a proportion of 50 g./sq.m. from the following suspension, which has been ground for 6 hours in a ball-mill:

thermally treated Congo Copal 35 g. carbon black 0.5 g. montan wax 65 g. methanol 800 cc.

After a reflectographic exposure as described in example 5, the nonheated areas, i.e., the parts corresponding with the image markings of the original, can easily be rubbed away with water. In this way a grey negative image is obtained from the original.

EXAMPLE 7 A transparent paper support of 40 g./sq.m. is coated in a proportion of 50 g./sq.m. with a dispersion, which has been ground for 6 hours in a ball-mill and which consists of:

ethylcellulose 25 g. carbon black 0.5 g. beeswax 75 g. methanol 720 cc. methylene chloride 80 cc.

After having been exposed reflectographically by a flash lamp as described in example 2, the material is heated at 60 C. for 10 sec. while being held in contact with a sheet of common writing paper. On the latter a grey positive print is obtained from the original.

EXAMPLE 8 A subbed support of cellulose triacetate is coated with a solution of the following composition in a proportion of 85 g./sq.m.:

gelatin 60 g. 5% aqueous m-phenylenc dlumlnc IUO cc. water 805 cc.

5% aqueous formaldehyde 5 cc.

After drying, a heat-sensitive layer is applied thereto pro rata of 60 g./sq.m. from the following suspension, which has been ground for 1 hour in a vibrating ball-mill:

ethylcellulose (degree of substitution of ethoxy groups 2.45) 35 g. carbon black 0.5 g. stearic acid 65 g. methanol 800 cc.

After reflectographic flash exposure as described in example 2, the material is wetted for a short while with water and then for 15 sec. brought in contact with a receiving paper prepared by dipping common writing paper in a 5 percent solution of 2,4-dinitrophenylpyridinium chloride in ethanol and drying. A brown positive image is obtained on this receiving paper. By wetting the master again and pressing it repeatedly to fresh sheets of receiving paper, some four prints can be obtained from the original.

EXAMPLE 9 A transparent paper support weighting 40 g./sq.m. is coated with the following suspension in a proportion of 60 g./sq.m.:

ammonium alginate 4 g. ethanol 50 cc. water 490 cc. aqueous carbon black dispersion as described in example 2 0.5 g. 50% aqueous suspension of mineral wax having an average particle size varying between i and 4 ,u. and melting at 50 C. [20 cc.

After having been dried, this material is reflectographically exposed by means of an electronic flash lamp as described in example 2, then wetted with water and pressed against a sheet of common writing paper. After having separated the material therefrom, a black positive reproduction of the original is obtained on the receiving material.

EXAMPLE i0 japan paper support weighing l6 g.lsq.m. is coated with a dispersion obtained by grinding for 8 hours in a ball-mill the following substances:

copoly (styrene ally) carbon black 05 g.

polyethylene glycol having an average molecular weight of l0,000 20 g.

montan wax 70 g.

methanol 600 cc.

Coating is carried out in such a way that after drying l0 g. of solid matter is present per sq.m. of Japan paper. The stencil material obtained is irradiated with flashlight as described in example 10. Without any further treatment several positive prints can be obtained in stencil printing with this master. EXAMPLE ll A dispersion consisting of:

cellulose acetate-sorbate 30 g. carbon black 05 g. montan wax 70 g. a mixture consisting of) parts of ethanol and l part of ethyl acetate 800 cc.

is ground for 6 hours in a ball-mill and then coated on an aluminum plate. Coating is carried out in such a way that after having been dried the layer possesses a thickness of 7 a. A transparent negative to be copied is then laid with its backside onto the heat-sensitive plate and the whole is irradiated by means of an electronic flash lamp having an energy output of 0.75 Watt.sec./sq.cm. The plate is then rubbed by means of a plug of wadding soaked with a 1 percent aqueous solution of sodium hydroxide. In this way the nonheated parts of the composition are eliminated from the plate and the subjacent metal parts are rendered strongly hydrophilic. The treated plate can now he used as an offset printing plate. by means of which positive prints can be obtained.

EXAMPLE 12 Common paper of 60 g./sq.m. is coated in a proportion of 50 g./sq.m. with the following dispersion, which has been ground for 6 hours in a ball-mill:

ethylcellulose (degree of substitution of ethoxy groups: 2.45) 4 g, stearic acid 70 carbon black 0.5 g. ethanol 800 cc.

After flash exposure through a transparent positive original in the same way as described in example 12 the paper is wetted with an aqueous methylene blue solution as described in example 10. Since the dye solution can only penetrate the paper at the nonheated parts of the heat-sensitive layer, a positive image is obtained from the original.

EXAMPLE 13 A subbed cellulose triacetate film is coated in a proportion of 80 g./sq.m. with the barium sulfate dispersion described in example 2. After drying, a heat-sensitive layer is applied thereto in a proportion of 50 g./sq.m. from the following suspension, which has been ground for 7 hours in a ball-mill:

copoly(vinyl acetate/crotonic acid) 210/20 35 g. carbon black 0.5 g. montan wax 65 g. methanol 800 cc.

The material obtained is irradiated with flash light in the way described in example 10 and can then be used as a master hydrotype printing. For this purpose an ink paste is used, which is prepared as follows:

75 g. of a carbon black dispersion containing per 100 g. 53 g. of carbon black, 23 g. of water, 18 g. of glycol, and 6 g. of nonylphenyl polyethylene oxide (containing 15 ethylene oxide units) are mixed with 225 g. of a 20 percent aqueous solution of cellulose acetophthaiate (degree of substitution of acetyl groups 1.3 to 1.5, degree of substitution of phthalyl groups 0.9 to 1.2; viscosity 12 cps., measured at 20 C. as a 3 percent solution in a mixture of 35 cc. of methyiglycol, 60 cc. of ethanol and cc. of acetone), g. of magnesium chloride, and 10 g. of 1,6-hexanediol. While strongly stirring a mixture of l 10 g. of white spirit (boiling range 140-200 C.) and 30 g. of xylene are added to the first mixture. In the paste obtained the dispersion of the oleophilic phase in the aqueous phase remains stable.

EXAMPLE 14 A subbed cellulose triacetate support is coated with a heatsensitive layer pro rate of 50 g./sq.m. from a coating compost tion prepared by grinding the following substances for 6 hours in a ball-mill: I

shellac 40 g. carbon black 0.5 g. pentaerytbritol ester of stearic acid 60 g. methanol 800 cc.

After having been dried, the resulting material is exposed by balsam colophonium 40 g. Carlille wax melting at 163 C. 60 carbon black 0.5 g. methanol 800 cc.

After having been dried, the heat-sensitive material is reflectographically exposed as described in example 1, but with an energy intensity of 0.98 Watt.sec. per sq.cm. Subsequently a paper wetted with methanol is pressed against the exposed heat-sensitive layer and then immediately separated therefrom. A dark grey positive image is obtained from the original on the paper. By repeating the latter steps some 5 copies having the same quality can be produced.

EXAMPLE 16 A subbed polyethylene terephthalate support is coated pro rata of g./sq.m. with a composition prepared as follows:

30 g. of copoly(ethylene/vinyl acetate) (67/33) are dissolved in 1,600 cc. of hot cyclohexane; after cooling, l g. of carbon black and 130 g. of carnauba wax are added and the composition is ball-milled for 6 hr.

A graphic paper original in contact with the heat-sensitive layer is reflectographically exposed with a flash lamp irradiating the heat-sensitive layer with an energy of 0.53 Watt.sec. per sq.cm. in 8.10" seconds. The exposed material is suited for use as hydrotype master. As printing ink the following composition is used:

aqueous carbon black dispersion containing pro g. 53 g. ofcarbon black, 23 g. of water, 18 g. of glycol and 6 g. of nonyiphenylpolythylenc oxide 100 g. zein I] g. triethylene glycol 36 cc. white spirit (boiling range 140 200 C.) 100 cc. paraffin oil 20 cc.

On a common direct planographic printing machine several hundred prints on ordinary paper are produced, without indication of any degradation of the printing quality.

EXAMPLE 17 Ordinary carbon paper for spirit duplicating purposes is coated over its carbon layer pro rata of 60 cc. per sq.m. with a dispersion of the following composition which was ball-milled for 6 hr.:

carnauba wax 130 g. copoly(styrene/n-butyl acrylate (50/50) 70 g. carbon black I g. cyclohexane 1600 cc.

After drying the material is exposed as described in example 10 and applied as spirit duplicating master. Up till 100 legible sharp copies of the original are obtained. A carbon layer with which useful results are obtained is prepared as follows:

50 g. of carnauba wax, 25 g. of montan wax and 25 g. of

beeswax are heated to 100 C. While slowly being stirred, a solution of 100 g. of crystal violet in cc. of ethanol is added to the melt, whereupon stirring and heating is continued till complete evaporization of the ethanol. Thereupon 100 cc. of paraffin oil are added and the hot liquid composition is coated onto a medium porous paper base. EXAMPLE 18 A subbed cellulose triacetate support is coated with the following composition pro rata of 75 cc. per sq.m., which composition has been ground for 6 hr. in a ball-mill:

ethylcellulose (degree of substitution of ethoxy groups: 2.45) 35 g. bleached montan wax 55 g. poly(isobutylene) (average molecular weight: 150,000) 10 g. methanol 800 cc.

After drying the wax-containing layer is coated with a surface layer from the following composition:

l% aqueous solution ofgelatin 1% aqueous solution of polyoxyethylene (viscosity at 25 C. oh: 5% aqueous solution is 300 cps.) 400 cc.

out at the same time.

We claim:

1. A method for reproducing an original having image markings of radiation-absorbing material, which method comprises the step of uniformly exposing to electromagnetic radiation, a recording material comprising at least one recording layer formed by a substantially opaque dispersion of a hydrophilic binder of finely divided particles of a hydrophobic nonpolymeric fatty or waxy material which is solid at room temperature, said finely divide material forming with the binder upon heating a substantially compatible mixture of significantly increased light-transparency, said recording layer also having uniformly distributed therethrough at least one finely divided pigment adapted to absorb at least part of electromagnetic radiation impinged thereon and convert such absorbed radiation into heat internally within said layer, said exposure being carried out while said recording layer is in direct heat conductive relation with the image markings of said original with a radiation source of sufficient intensity and for a time of such duration up to seconds that as a consequence of the generation of heat by said pigment a pattern corresponding to the nonimage areas of said is produced in said layer having increased transparency and decreased hydrophlity, the area of said layer corresponding to the image of said original remaining substantially unchanged.

2. A method according to claim 1, wherein said recording layer is prepared from a dispersion of said relatively hydrophobic material in a hydrophilic binder, the ratio by weight of dispersed hydrophobic material to hydrophilic binder being at least 1:4 and at most 25: l.

3. A method according to claim 1, wherein the dispersed hydrophobic material is composed of waxlike particles.

4. A method according to claim 1, wherein said hydrophobic particles size from 0.01 p. to 50;.

5. A method according to claim 1, wherein said pigment is carbon black.

6. A method according to claim 1, wherein said pigment is present in the recording layer in an amount imparting thereto an optical density varying between 0.2 to l.

7. A method according to claim 1, wherein the exposure is carried out by means of electromagnetic radiation containing visible light.

8. A method for recording or reproducing information ac cording to claim 7, wherein the electromagnetic radiation contains at least 30 percent of the energy in the wavelength range below 700 mg.

9. A method for recording or reproducing information according to claim 8, wherein the exposure is carried out at an intensity of at least 0.1 Watt-sec. per sq. cm. for an exposure time of no more than 10 second. 

2. A method according to claim 1, wherein said recording layer is prepared from a dispersion of said relatively hydrophobic material in a hydrophilic binder, the ratio by weight of dispersed hydrophobic material to hydrophilic binder being at least 1:4 and at most 25:1.
 3. A method according to claim 1, wherein the dispersed hydrophobic material is composed of waxlike particles.
 4. A method according to claim 1, wherein said hydrophobic particles size from 0.01 Mu to 50 Mu .
 5. A method according to claim 1, wherein said pigment is carbon black.
 6. A method according to claim 1, wherein said pigment is present in the recording layer in an amount imparting thereto an optical density varying between 0.2 to
 1. 7. A method according to claim 1, wherein the exposure is carried out by means of electromagnetiC radiation containing visible light.
 8. A method for recording or reproducing information according to claim 7, wherein the electromagnetic radiation contains at least 30 percent of the energy in the wavelength range below 700 m Mu .
 9. A method for recording or reproducing information according to claim 8, wherein the exposure is carried out at an intensity of at least 0.1 Watt-sec. per sq. cm. for an exposure time of no more than 10 1 second. 